This invention relates to a method and apparatus for generation of single-pulse ultrasonic signals at selectable pulse repetition rates.
Ultrasonic signals are typically generated by stressing a piezoelectric material with sinusoidal electrical signal. When the electrical signal is terminated, the transducer continues to ring in damped oscillation over several cycles. The length of the electrical signal plus the ringing period determines the duration of the output ultrasonic signal, commonly referred to as a pulse, although in fact consists of many cycles of a sinusoidal wave. The width of this pulse limits temporal resolution when used in nondestructive testing, complicates its use in depth-finding, and limits the minimum usable depth. Additionally, the major power limitation in depth-finding usage is cavitation at the transducer surface. It would be desirable to generate an output pulse of minimum width using a conventional piezoelectric ultrasonic transducer.